1. Field of the Invention
The invention relates to an appliance for the dispensing of bulk material.
2. Background Information
Known appliances for dispensing of bulk material consist of a rotor with radial blades which rotates in a cylindrical housing about a vertical axis and which is covered on its topside by a stationary cover plate provided with perforations for the bulk-material inflow and on its underside by an associated stationary lower cover plate with a discharge orifice, the upper and lower discharge orifices being arranged offset relative to one another at a rotary angle of 180.degree.. Dispensing appliances of this type are designated as horizontal-discharge cellular-wheel sluices.
DE 3,544,014 A 1 has made known a cellular-wheel sluice of this type which serves to convey bulk material out of a space of a pressure of any amount into a space of equal, higher or lower pressure. The cellular-wheel rotor rotating about a vertical axis forms receiving pockets for the bulk material which are filled with the bulk material on the topside of the cellular-wheel sluice and which are emptied on the underside after a rotation of approximately 180.degree..
Cellular-wheel sluices with rotors rotating about a horizontal axis, which work in fundamentally the same way as described above, are also known.
Cellular-wheel sluices of this type are connected on their discharge side to conveying lines which are under a conveying pressure. However, because of considerable leakage losses in the cellular-wheel sluice, it has not been possible for the pressure and air quantity of these conveying lines to be maintained at the desired level. This is all the more so when a plurality of such cellular-wheel sluices are arranged in succession above a common conveying line, for the purpose of conveying out of various silos.
Leakage losses occur in a cellular-wheel sluice with a rotating rotor as a result of unavoidable gaps both between the rotating rotor and the lower and upper cover plates and between the rotating rotor and the cylinder wall of the rotor housing. Although a high outlay for sealing off these gaps and keeping them small keeps the leakage loss within limits, nevertheless, on account of these leakage losses, the use of cellular-wheel sluices of this kind has been economical only up to an overpressure in the conveying line of the order of approximately 1 bar.
Furthermore, from DE 3,035,048 C 2 is known a dispensing appliance, in which rotating upper and lower cover plates are used instead of a rotating cellular wheel. The cellular housing thus remains stationary. The bulk material is supplied via an upper rotating cover plate with a feed orifice in the form of a segment of a circle. Likewise, the bulk material is discharged from the stationary cells via a lower rotating cover plate with a discharge orifice located opposite the upper feed orifice. The advantage of this dispensing appliance in relation to those with a rotating cellular wheel is that the gap length and, for the same gap width, therefore also the gap area, are considerably reduced, since there is no longer a rotating cellular wheel with corresponding vertical gaps. Instead, here there need only be a horizontal sealing in the upper and lower regions of the rotating cover plates in relation to the cellular housing. A dispensing appliance of this type therefore makes it possible to employ higher conveying pressures or pressure differences between the conveying line below and the silo above the cellular-wheel sluice.
A disadvantage of this known appliance with a stationary cellular housing is the expensive mechanism for executing the rotational movement of the upper and lower cover plates. The drive of the central driving shaft and its expensive mounting and sealing necessitate complicated production involving a high outlay. Moreover, this drive takes up a large part of the central region of the cellular housing. Furthermore, a driving shaft has to be guided radially outwards. In addition to the complicated drive, a dispensing appliance of this type is also difficult to clean, since a dismantling of the individual drive components under practical conditions is extremely complicated and involves a high outlay.
Dispensing appliances having an eccentric drive have become known from US-RE 29,347 or GB 2,166,714 A. In the first-mentioned publication, both the cellular wheel and the two cover plates are driven via a gear. The relationship between these drives affords the conveying power of the dispensing appliance. The dispensing appliance according to GB 2,166,714 contains no chambers in the form of a segment of a circle and is not suitable for conveying relatively large quantities. The drive of the two cover plates takes place in a similar way to DE 3,025,048 C 2 by means of a central shaft.